The manufacture of tape cartridges involves the assembly of precision components which enable magnetic recording tape to be operated in the tape cartridge in a manner achieving very high areal recording densities. Such product performance requirements are increasingly rigorous in the areas of speed and capacity. These performance characteristics are determined by various component related features. A particularly important component is the tape cartridge base plate. The base plate topography affects the perpendicularity of pins mounted in the base plate. These pins support other components of the tape cartridge, which in turn affect the performance obtained from a tape moving in the tape cartridge.
The designers and manufacturers of tape cartridge base plates have focused on improved flatness and rigidity as primary features in controlling the quality of base plates. Other focus areas involve the methods of forming and blanking the metal used in the manufacture of the base plates.
This invention provides a new and different approach to controlling base plate quality, particularly to the flatness of the base plate. In brief summary, a tape cartridge of the present invention comprises a flat metallic base plate comprising an aluminum alloy, and component parts mounted on the plate, including pins that are nominally perpendicular to the plate and which support and facilitate tape transfer within the cartridge. The base plate comprises an aluminum alloy having a yield stress in the range from 25,000 to 30,000 psi.
Within the present invention, the shear properties of an aluminum alloy base plate can be improved by adjusting the composition of the aluminum alloy. A composition shown to produce base plates with desired shear properties comprises from about 0.5 to 3 parts by weight silicon and from about 0.1 to 0.7 parts by weight iron, based on 100 parts of aluminum alloy. The aluminum alloy of the present invention may optionally comprise one or more of the following: up to about 1 part by weight Mn; up to about 2 parts by weight Mg; and mixtures thereof; based on 100 parts of aluminum alloy.
The present invention further provides a tape cartridge base plate comprising the above-described aluminum alloy.